Twin-tube damper

Abstract

A twin-tube damper includes an outer cylinder with a lower mounting cap at a lower end of the outer cylinder and an upper cap at an upper end of the outer cylinder. An inner cylinder is concentrically arranged within the outer cylinder between the upper cap and the lower mounting cap. A reserve reservoir is defined by the annular volume between the outer cylinder and the inner cylinder. A piston rod extends to a piston head within the inner cylinder. A base is seated in a lower end of the inner cylinder, wherein the base includes valves which allow hydraulic fluid to flow between the compression reservoir and the reserve reservoir during the extension stroke and the rebound stroke. At least one passage is defined through the upper cap in combination with a check valve that only allows one-way fluid transfer from the reserve reservoir to the rebound reservoir.

1 . A twin-tube damper, comprising:
 a. an outer cylinder, a lower mounting cap at a lower end of the outer cylinder and an upper cap at an upper end of the outer cylinder;   b. an inner cylinder concentrically arranged within the outer cylinder between the upper cap and the lower mounting cap;   c. a reserve reservoir defined by an annular volume between the outer cylinder and the inner cylinder,   d, wherein the twin-tube damper is filled with a hydraulic fluid;   e. a piston rod extending downward from a top end through a rod-guide passage in the upper cap to a piston head within the inner cylinder, wherein the piston head divides an interior volume of the inner cylinder into a compression reservoir below the piston head and a rebound reservoir above the piston head, wherein the piston head and shaft are arranged to slidably reciprocate relative to the inner cylinder during a compression stroke and a rebound stroke;   f. a base seated in a lower end of the inner cylinder, wherein the base includes valves which allow hydraulic fluid to flow between the compression reservoir and the reserve reservoir during the compression stroke and the rebound stroke;   g. the upper cap including an upper portion engaging an upper end portion of the outer cylinder, and a lower portion engaging an upper end portion of the inner cylinder and wherein the lower portion defines a lower surface in communication with the rebound reservoir;   h. a stepped portion extending between the upper portion and the lower portion, the stepped portion in communication with the reserve reservoir; and   i. at least one passage defined through the upper cap in combination with a check valve that only allows one-way fluid transfer from the reserve reservoir to the rebound reservoir.   
     
     
         2 . The twin-tube damper of  claim 1 , comprising a plurality of passages defined through the upper cap, wherein each passage only allows one-way fluid transfer from the reserve reservoir to the rebound reservoir. 
     
     
         3 . The twin-tube damper of  claim 1 , wherein the stepped portion includes a ring-shaped downward facing surface. 
     
     
         4 . The twin-tube damper of  claim 1 , including a recessed portion defined in the upper portion, wherein the recessed portion defines a volume in communication with the reserve reservoir and a pipe forming the at least one passage. 
     
     
         5 . The twin-tube damper of  claim 4 ,
 a. wherein the pipe connects to a cup-shaped portion having an open lower end in communication with the rebound reservoir;   b. the cup-shaped portion having a cylindrical sidewall with a diameter larger the diameter of the pipe and a ring-shaped tapered portion extending between the sidewall and the lower end of the pipe; and   c. a check-valve stopper arranged within the cup-shaped portion.   
     
     
         6 . The twin-tube damper of  claim 5 , wherein the check-valve stopper is a spherical ball. 
     
     
         7 . The twin-tube damper of  claim 1 , wherein the piston head includes adjustable piston head valves. 
     
     
         8 . The twin-tube damper of  claim 7 , wherein the piston valves comprise unidirectional piston head valves in one direction with different flow parameters than unidirectional piston head valves in the opposite direction. 
     
     
         9 . The twin-tube damper of  claim 7 , wherein the base includes adjustable base valves. 
     
     
         10 . The twin-tube damper of  claim 1 , wherein during a compression stroke, hydraulic fluid flows from the reserve reservoir into the rebound reservoir at a rate less than or equal to the rate that hydraulic fluid flows into the reserve reservoir from the compression reservoir, and wherein during a rebound stroke, fluid is prevented from flowing from the rebound reservoir into the reserve reservoir. 
     
     
         11 . A twin-tube damper, comprising:
 a. an outer cylinder having an upper end and a lower end;   b. a lower mounting cap at the lower end of the outer cylinder, the lower mounting cap defining a lower attachment point;   c. an upper cap at the upper end of the outer cylinder;   d. an inner cylinder concentrically arranged within the outer cylinder between the upper cap and the lower mounting cap;   e. a reserve reservoir defined by an annular volume between the outer cylinder and the inner cylinder;   f. a top mounting end defining an upper attachment point;   g. a piston rod extending downward from the top mounting end and slidably extending through a rod-guide passage in the upper cap to a lower end located in an interior of the inner cylinder;   h. a piston head mounted to the lower end of the piston rod, wherein a perimeter of the piston head slidably engages an inner wall of the inner cylinder, and wherein the piston head divides an interior volume of the inner cylinder into a compression reservoir below the piston head and a rebound reservoir above the piston head;   i. a base seated in a lower end of the inner cylinder between the inner cylinder and the lower mounting cap, wherein the base includes valves which allow hydraulic fluid to flow between the compression reservoir and the reserve reservoir during the respective compression and rebound strokes of the twin-tube damper;   j. the upper cap including a body with an upper diameter portion in sealed engagement with the upper end and an inner wall of the outer cylinder, and a lower diameter portion which extends into and is in sealed engagement with an upper end and the inner wall of the inner cylinder wherein the lower diameter portion includes a lower surface in communication with the rebound reservoir;   k. the body including a stepped portion between the upper diameter portion and the lower diameter portion, the stepped portion defining a downward facing surface in communication with the reserve reservoir; and   l. a one-way passage defined through the upper cap that only allows fluid transfer from the reserve reservoir into the rebound reservoir.   
     
     
         12 . The twin-tube damper of  claim 11 , comprising a plurality of passages defined through the upper cap in combination with check valves, wherein each passage allows one-way fluid transfer from the reserve reservoir to the rebound reservoir. 
     
     
         13 . The twin-tube damper of  claim 11 , wherein the stepped portion includes a ring-shaped downward facing surface. 
     
     
         14 . The twin-tube damper of  claim 11 , wherein the one-way passage includes a pipe with an orifice in communication with the reserve reservoir, wherein the pipe connects to a cup-shaped portion having an open lower end in communication with the rebound reservoir, and a check-valve stopper arranged within the cup-shaped portion. 
     
     
         15 . The twin-tube damper of  claim 11 , wherein the piston head includes adjustable piston head valves. 
     
     
         16 . The twin-tube damper of  claim 15 , wherein the piston head valves comprise unidirectional piston head valves in one direction with different flow parameters than unidirectional piston head valves in the opposite direction. 
     
     
         17 . The twin-tube damper of  claim 15 , wherein the base includes adjustable base valves. 
     
     
         18 . A twin-tube damper, comprising:
 a. an outer cylinder with a lower mounting cap at a lower end of the outer cylinder and an upper cap at an upper end of the outer cylinder;   b. an inner cylinder concentrically arranged within the outer cylinder between the upper cap and the lower mounting cap;   c. a reserve reservoir defined by an annular volume between the outer cylinder and the inner cylinder, wherein the inner cylinder and the reserve reservoir are filled with hydraulic fluid;   d. a piston rod extending downward from a top end through a rod-guide passage in the upper cap to a piston head within the inner cylinder, wherein the piston head divides an interior volume of the inner cylinder into a compression reservoir below the piston head and a rebound reservoir above the piston head, wherein the piston head and shaft are arranged to slidably reciprocate relative to the inner cylinder during a compression stroke and a rebound stroke;   e. a base seated in a lower end of the inner cylinder, wherein the base includes base valves which allow hydraulic fluid to flow between the compression reservoir and the reserve reservoir;   f. the upper cap engaging an upper end portion of the outer cylinder and engaging an upper end portion of the inner cylinder; and,   g. at least one one-way passage defined through the upper cap, wherein during the compression stroke, hydraulic fluid flows from the reserve reservoir into the rebound reservoir through the one-way passage at the same rate that hydraulic fluid flows through the base valves into the reserve reservoir from the compression reservoir, and wherein during a rebound stroke, fluid is prevented from flowing from the rebound reservoir into the reserve reservoir.   
     
     
         19 . The twin-tube damper of  claim 18 , wherein the base includes adjustable base valves. 
     
     
         20 . The twin-tube damper of  claim 19 , wherein the piston head includes adjustable piston head valves.